In various integrated circuits a vertical dielectric layer is implemented. A “vertical dielectric layer” is a dielectric layer that extends in a vertical direction of a semiconductor body in which the circuit is integrated. The vertical dielectric layer may be used to dielectrically insulate different semiconductor devices of the circuit. In a new type of MOS transistor, a dielectric layer extends along a drift region of the MOS transistor and dielectrically insulates the drift region from a drift control region, where the drift control region serves to control a conducting channel in the drift region along the dielectric layer.
According to a known method, a vertical dielectric layer can be produced by forming a trench in the semiconductor body, forming the dielectric layer on at least one sidewall of trench and filling the trench with a monocrystalline semiconductor material. However, the dielectric layer may have a poor adhesion to the monocrystalline “filling material” and a huge number of oxide charges may be trapped along the interface between the dielectric layer and the semiconductor material. Thus, the dielectric layer may be removed using an etching technique and may be replaced by another dielectric layer formed by an oxidation step.
An etching technique, however, may be critical in those cases in which there is a horizontal dielectric layer arranged in the semiconductor body that adjoins the vertical dielectric layer. Etching the vertical layer would also partially etch the horizontal layer, which is undesirable.
There is, therefore, a need for an improved method for producing a semiconductor device including a dielectric layer, in particular a vertical dielectric layer.